<title>[Usaco2006 Jan] Redundant Paths 分离的路径</title><link href="http://hzoi.com/tomorrow.css" rel="stylesheet"><div class="ui existing segment"><pre><code><span class="pl-cp">#ifdef debug</span>
<span class="pl-cp">#define DEBUG(fmt, ...)                                                    \</span>
<span class="pl-cp">    printf(&quot;\033[33;1m[DEBUG]\033[34m%s:%d\033[0m : &quot; #fmt &quot;\n&quot;, __FILE__, \</span>
<span class="pl-cp">           __LINE__, ##__VA_ARGS__)</span>
<span class="pl-cp">#define WARNIF(exp, fmt, ...)                                               \</span>
<span class="pl-cp">    if (exp)                                                                \</span>
<span class="pl-cp">        printf(&quot;\033[31;1m[WARNING `&quot; #exp &quot;`]\033[34m%s:%d\033[0m : &quot; #fmt \</span>
<span class="pl-cp">               &quot;\n&quot;,                                                        \</span>
<span class="pl-cp">               __FILE__, __LINE__, ##__VA_ARGS__);</span>
<span class="pl-cp">#else</span>
<span class="pl-cp">#define DEBUG(fmt, ...)</span>
<span class="pl-cp">#define WARNIF(exp, fmt, ...)</span>
<span class="pl-cp">#endif</span>
<span class="pl-cp">#include</span> <span class="pl-cpf">&lt;algorithm&gt;</span><span class="pl-cp"></span>
<span class="pl-cp">#include</span> <span class="pl-cpf">&lt;cstdio&gt;</span><span class="pl-cp"></span>
<span class="pl-cp">#define M 10005</span>
<span class="pl-cp">#define N 5005</span>
<span class="pl-k">using</span> <span class="pl-k">namespace</span> <span class="pl-n">std</span><span class="pl-p">;</span>
<span class="pl-kt">int</span> <span class="pl-n">n</span><span class="pl-p">,</span> <span class="pl-n">m</span><span class="pl-p">,</span> <span class="pl-n">vis</span><span class="pl-p">[</span><span class="pl-n">M</span> <span class="pl-o">&lt;&lt;</span> <span class="pl-mi">1</span><span class="pl-p">],</span> <span class="pl-n">du</span><span class="pl-p">[</span><span class="pl-n">N</span><span class="pl-p">],</span> <span class="pl-n">ans</span><span class="pl-p">;</span>
<span class="pl-kt">int</span> <span class="pl-n">cnt</span> <span class="pl-o">=</span> <span class="pl-mi">1</span><span class="pl-p">,</span> <span class="pl-n">head</span><span class="pl-p">[</span><span class="pl-n">N</span><span class="pl-p">],</span> <span class="pl-n">u</span><span class="pl-p">[</span><span class="pl-n">M</span><span class="pl-p">],</span> <span class="pl-n">v</span><span class="pl-p">[</span><span class="pl-n">M</span><span class="pl-p">];</span>
<span class="pl-kt">int</span> <span class="pl-n">now</span><span class="pl-p">,</span> <span class="pl-n">top</span><span class="pl-p">,</span> <span class="pl-n">col</span><span class="pl-p">,</span> <span class="pl-n">dfn</span><span class="pl-p">[</span><span class="pl-n">N</span><span class="pl-p">],</span> <span class="pl-n">low</span><span class="pl-p">[</span><span class="pl-n">N</span><span class="pl-p">],</span> <span class="pl-n">sta</span><span class="pl-p">[</span><span class="pl-n">N</span><span class="pl-p">],</span> <span class="pl-n">color</span><span class="pl-p">[</span><span class="pl-n">N</span><span class="pl-p">];</span>
<span class="pl-k">struct</span> <span class="pl-n">edge</span> <span class="pl-p">{</span>
    <span class="pl-kt">int</span> <span class="pl-n">next</span><span class="pl-p">,</span> <span class="pl-n">to</span><span class="pl-p">;</span>
<span class="pl-p">}</span> <span class="pl-n">e</span><span class="pl-p">[</span><span class="pl-n">M</span> <span class="pl-o">&lt;&lt;</span> <span class="pl-mi">1</span><span class="pl-p">];</span>

<span class="pl-kt">void</span> <span class="pl-nf">add</span><span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">u</span><span class="pl-p">,</span> <span class="pl-kt">int</span> <span class="pl-n">v</span><span class="pl-p">)</span> <span class="pl-p">{</span>
    <span class="pl-n">cnt</span><span class="pl-o">++</span><span class="pl-p">;</span>
    <span class="pl-n">e</span><span class="pl-p">[</span><span class="pl-n">cnt</span><span class="pl-p">].</span><span class="pl-n">next</span> <span class="pl-o">=</span> <span class="pl-n">head</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">];</span>
    <span class="pl-n">e</span><span class="pl-p">[</span><span class="pl-n">cnt</span><span class="pl-p">].</span><span class="pl-n">to</span> <span class="pl-o">=</span> <span class="pl-n">v</span><span class="pl-p">;</span>
    <span class="pl-n">head</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-n">cnt</span><span class="pl-p">;</span>
    <span class="pl-n">cnt</span><span class="pl-o">++</span><span class="pl-p">;</span>
    <span class="pl-n">e</span><span class="pl-p">[</span><span class="pl-n">cnt</span><span class="pl-p">].</span><span class="pl-n">next</span> <span class="pl-o">=</span> <span class="pl-n">head</span><span class="pl-p">[</span><span class="pl-n">v</span><span class="pl-p">];</span>
    <span class="pl-n">e</span><span class="pl-p">[</span><span class="pl-n">cnt</span><span class="pl-p">].</span><span class="pl-n">to</span> <span class="pl-o">=</span> <span class="pl-n">u</span><span class="pl-p">;</span>
    <span class="pl-n">head</span><span class="pl-p">[</span><span class="pl-n">v</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-n">cnt</span><span class="pl-p">;</span>
<span class="pl-p">}</span>

<span class="pl-kt">void</span> <span class="pl-nf">tarjan</span><span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">u</span><span class="pl-p">)</span> <span class="pl-p">{</span>
    <span class="pl-n">dfn</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-n">low</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-o">++</span><span class="pl-n">now</span><span class="pl-p">;</span>
    <span class="pl-n">sta</span><span class="pl-p">[</span><span class="pl-o">++</span><span class="pl-n">top</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-n">u</span><span class="pl-p">;</span>
    <span class="pl-k">for</span> <span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">i</span> <span class="pl-o">=</span> <span class="pl-n">head</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">];</span> <span class="pl-n">i</span><span class="pl-p">;</span> <span class="pl-n">i</span> <span class="pl-o">=</span> <span class="pl-n">e</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">].</span><span class="pl-n">next</span><span class="pl-p">)</span>
        <span class="pl-k">if</span> <span class="pl-p">(</span><span class="pl-o">!</span><span class="pl-n">vis</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">])</span> <span class="pl-p">{</span>
            <span class="pl-n">vis</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-n">vis</span><span class="pl-p">[</span><span class="pl-n">i</span> <span class="pl-o">^</span> <span class="pl-mi">1</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-mi">1</span><span class="pl-p">;</span>
            <span class="pl-k">if</span> <span class="pl-p">(</span><span class="pl-o">!</span><span class="pl-n">dfn</span><span class="pl-p">[</span><span class="pl-n">e</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">].</span><span class="pl-n">to</span><span class="pl-p">])</span> <span class="pl-p">{</span>
                <span class="pl-n">tarjan</span><span class="pl-p">(</span><span class="pl-n">e</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">].</span><span class="pl-n">to</span><span class="pl-p">);</span>
                <span class="pl-n">low</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-n">min</span><span class="pl-p">(</span><span class="pl-n">low</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">],</span> <span class="pl-n">low</span><span class="pl-p">[</span><span class="pl-n">e</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">].</span><span class="pl-n">to</span><span class="pl-p">]);</span>
            <span class="pl-p">}</span> <span class="pl-k">else</span>
                <span class="pl-n">low</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-n">min</span><span class="pl-p">(</span><span class="pl-n">low</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">],</span> <span class="pl-n">dfn</span><span class="pl-p">[</span><span class="pl-n">e</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">].</span><span class="pl-n">to</span><span class="pl-p">]);</span>
        <span class="pl-p">}</span>
    <span class="pl-k">if</span> <span class="pl-p">(</span><span class="pl-n">low</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">]</span> <span class="pl-o">==</span> <span class="pl-n">dfn</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">])</span> <span class="pl-p">{</span>
        <span class="pl-n">color</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">]</span> <span class="pl-o">=</span> <span class="pl-o">++</span><span class="pl-n">col</span><span class="pl-p">;</span>
        <span class="pl-k">while</span> <span class="pl-p">(</span><span class="pl-n">sta</span><span class="pl-p">[</span><span class="pl-n">top</span><span class="pl-p">]</span> <span class="pl-o">!=</span> <span class="pl-n">u</span><span class="pl-p">)</span> <span class="pl-p">{</span>
            <span class="pl-n">color</span><span class="pl-p">[</span><span class="pl-n">sta</span><span class="pl-p">[</span><span class="pl-n">top</span><span class="pl-p">]]</span> <span class="pl-o">=</span> <span class="pl-n">col</span><span class="pl-p">;</span>
            <span class="pl-n">top</span><span class="pl-o">--</span><span class="pl-p">;</span>
        <span class="pl-p">}</span>
        <span class="pl-n">top</span><span class="pl-o">--</span><span class="pl-p">;</span>
    <span class="pl-p">}</span>
<span class="pl-p">}</span>

<span class="pl-kt">int</span> <span class="pl-nf">main</span><span class="pl-p">()</span> <span class="pl-p">{</span>
    <span class="pl-n">scanf</span><span class="pl-p">(</span><span class="pl-s">&quot;%d%d&quot;</span><span class="pl-p">,</span> <span class="pl-o">&amp;</span><span class="pl-n">n</span><span class="pl-p">,</span> <span class="pl-o">&amp;</span><span class="pl-n">m</span><span class="pl-p">);</span>
    <span class="pl-k">for</span> <span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">i</span> <span class="pl-o">=</span> <span class="pl-mi">1</span><span class="pl-p">;</span> <span class="pl-n">i</span> <span class="pl-o">&lt;=</span> <span class="pl-n">m</span><span class="pl-p">;</span> <span class="pl-o">++</span><span class="pl-n">i</span><span class="pl-p">)</span> <span class="pl-p">{</span>
        <span class="pl-n">scanf</span><span class="pl-p">(</span><span class="pl-s">&quot;%d%d&quot;</span><span class="pl-p">,</span> <span class="pl-o">&amp;</span><span class="pl-n">u</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">],</span> <span class="pl-o">&amp;</span><span class="pl-n">v</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">]);</span>
        <span class="pl-n">add</span><span class="pl-p">(</span><span class="pl-n">u</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">],</span> <span class="pl-n">v</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">]);</span>
    <span class="pl-p">}</span>
    <span class="pl-k">for</span> <span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">i</span> <span class="pl-o">=</span> <span class="pl-mi">1</span><span class="pl-p">;</span> <span class="pl-n">i</span> <span class="pl-o">&lt;=</span> <span class="pl-n">n</span><span class="pl-p">;</span> <span class="pl-o">++</span><span class="pl-n">i</span><span class="pl-p">)</span>
        <span class="pl-k">if</span> <span class="pl-p">(</span><span class="pl-o">!</span><span class="pl-n">dfn</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">])</span> <span class="pl-n">tarjan</span><span class="pl-p">(</span><span class="pl-n">i</span><span class="pl-p">);</span>
    <span class="pl-k">for</span> <span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">i</span> <span class="pl-o">=</span> <span class="pl-mi">1</span><span class="pl-p">;</span> <span class="pl-n">i</span> <span class="pl-o">&lt;=</span> <span class="pl-n">m</span><span class="pl-p">;</span> <span class="pl-o">++</span><span class="pl-n">i</span><span class="pl-p">)</span>
        <span class="pl-k">if</span> <span class="pl-p">(</span><span class="pl-n">color</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">]]</span> <span class="pl-o">!=</span> <span class="pl-n">color</span><span class="pl-p">[</span><span class="pl-n">v</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">]])</span> <span class="pl-p">{</span>
            <span class="pl-n">du</span><span class="pl-p">[</span><span class="pl-n">color</span><span class="pl-p">[</span><span class="pl-n">u</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">]]]</span><span class="pl-o">++</span><span class="pl-p">;</span>
            <span class="pl-n">du</span><span class="pl-p">[</span><span class="pl-n">color</span><span class="pl-p">[</span><span class="pl-n">v</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">]]]</span><span class="pl-o">++</span><span class="pl-p">;</span>
        <span class="pl-p">}</span>
    <span class="pl-k">for</span> <span class="pl-p">(</span><span class="pl-kt">int</span> <span class="pl-n">i</span> <span class="pl-o">=</span> <span class="pl-mi">1</span><span class="pl-p">;</span> <span class="pl-n">i</span> <span class="pl-o">&lt;=</span> <span class="pl-n">col</span><span class="pl-p">;</span> <span class="pl-o">++</span><span class="pl-n">i</span><span class="pl-p">)</span>
        <span class="pl-k">if</span> <span class="pl-p">(</span><span class="pl-n">du</span><span class="pl-p">[</span><span class="pl-n">i</span><span class="pl-p">]</span> <span class="pl-o">==</span> <span class="pl-mi">1</span><span class="pl-p">)</span> <span class="pl-n">ans</span><span class="pl-o">++</span><span class="pl-p">;</span>
    <span class="pl-n">printf</span><span class="pl-p">(</span><span class="pl-s">&quot;%d</span><span class="pl-se">\n</span><span class="pl-s">&quot;</span><span class="pl-p">,</span> <span class="pl-n">ans</span> <span class="pl-o">+</span> <span class="pl-mi">1</span> <span class="pl-o">&gt;&gt;</span> <span class="pl-mi">1</span><span class="pl-p">);</span>
    <span class="pl-k">return</span> <span class="pl-mi">0</span><span class="pl-p">;</span>
<span class="pl-p">}</span>
</cpde></pre></div>